A report on Gratidia sp. from Zaire (PSG 141), and a study of the hatching of the eggs

5 Pages·1996·2.1 MB·English

by  Ingo Fritzsche

A report on Gratidia sp. from Zaire (PSG 141), and a study of the
hatching of the eggs.
IngO Fritzsche, Huberstrasse 1, D-38855 Wernigerode, Germany.
Drawing ofegg by Oliver Zompro.
Abstract
Theadults ofan unidentified species ofGratidia from Zaire (PSG 41), are briefly described. The egg is illustrated
and dataon egg laying rates, incubationtime and hatch rates are presented.
Key words
Phasmida, Gratidia sp., rearing, eggs, laying, incubation, hatch rate.
Introduction
This species belongs to the family Heteronemiidae, sub-family Pachymorphinae, tribe
Gratidiini, and genus Gratidia Stal; the species is unidentified- This species was previously
referred to Romulus Saussure (see Bragg, 1995). A lot of species belongs to this genus and
thedetermination is very difficult, becausethe differences between the species are very slight.
The culture originated in Zaire.
Male
The male is about 50-58mm in length and has a colour varying from green to brown, with
a reddish mesothorax and metathorax. There is a green stripe on the mesothorax and
metathorax on both sides of the thorax. The legs are very long. The femora of the middle
and hind legs are greenish. The tibiae and tarsi are brownish. The coxa are greyish. There
are no spines on legs or body. The antennae are 13-14mm long with 17 segments and are
a beige colour. A lot of fine hairs are on the antennae. The head is beige and has a brown
stripe on each side. The abdominal apex is yellowish and as broad as the body. Two cerci
situated on the abdominal apex look like a hoop.
Female
It has a greenish or brown colour ofthe body, with a length ofabout 75-
80mm. The width of the 3rd and 4th abdominal segments is about 2.5-
3,0mm. The inter-segmental skin is white. The colour is very variable
depending on tl^ humidity in the cultures. The antennae are shorter than
the male’s antennae; they have 18 segments but are only 5-6mm long.
The sub-genital plate is very long, it reaches to the end of the abdomen.
The cerci are much longer than the end of the abdomen.
Nymphs
When the nymphs hatch they have a length of ll-13mm. The colour is
yellowish or pde yellow-white. The body is like a thread. The nymphs
change their skin 6 or 7 times. After 4 months they are adults.
Eggs
The eggs have a lengths of4.6mm and a width of 1.0mm and a height of
1,2mm. An egg in profile lets us see that the operculum is tilted towards
the micropylar plate (fig. 1). The colour is beige. The operculum is flat
Figure 1.
with irregular marks. On the sides ofthe operculum we can finda crown Egg of PSG 141.
ofspines. The micropylar plate is a very small ellipse, which is enclosed
by a strip running from the operculum edge to the polar end. The eggs
are glued to the side of the cage or to the foodplant.
Phasmid Studies, 5(1): 13
The laying and hatchingdatesforonefemale
—
—— — — — — — —
--- - - - - ... ....... . —
February 1 2 3 4 6 6 7 8 9 io 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
laid adu cop cop 2 3 2 2
hatched 3 2 1
inApril 23 23 26
inApril 23 24
InApril -
--- -- -
March 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
laid 4 2 4 2 3 3 0 2 2 3 3 2 2 3 3 4 4 4 4 5 3 0 2 4 3 5 5 0 6 1 3
hatched i 2 1 3 0 i i 1 3 1 4 2 i d 1 2 6 2
in May f 4 2 2 6 8 12 a fa ff 13 20 18 20 fa
7 4 10 f2 13 20 2f
7 10 12 22
20 22
— —27
in June --- -- f f -
April 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
laid 2 4 2 2 4 2 2 0 3 2 3 4 3 2 2 3 4 2 4 3 3 3 3 2 0 3 2 2 2 4
hatched 1 i 2 2 2 i 1 2 2 2 3 i 1 2 2 1 1 3 i 2 i 4
In May 28 25 30
in June f 6 6 4 7 7 7 9 fO 7 9 13 f4 f7 f7 22 f7 22 23 23
6 9 9 ff ff 11 13 f7 25 27 23
12 25 29
inJuly 2
May 1 2 3 4 6 6 7 8 9 10 11 12 13 14 15 16 17 18 20 21 22 23 24 25 26 27 28 29 30 31
laid 2 2 4 1 3 1 2 1 4 4 4 5 2 0 4 1 3 0 2 2 5 3 4 3 2 0 2 3 3 4 1
14
hatched 1 1 1 2 1 1 0 1 0 1 3 0 2 1 1 1
inJune 18 30 30 30 5(1):
In—July 3 3 4 6 a a 9 2f fa 20
— — f2 2f ——
—
— 12 Studies,
- - -
Fritzfiche
June 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27* 28 29 30
laid 2 dead Phastrid
Ingo hatched
»
PSG 141, Grandia sp.: a study ofegg laying and incubation
Egg laying behaviour
The female searches with her front legs and the antennae for a good place for the egg. Ifshe
has found one, she bends her abdomen end between the antennae, over her thorax. The
antennae place the eggs in the right position; the legs help them, but the most work is done
by the antennae. Usually Grandia lays her eggs in the same place, so we can find in a cage
a lot of eggs in the same place.
Defence reaction
When concerned the phasmids form a ball for the first defence reaction. All legs, the
abdomen and the thorax form a ball. The legs get lifted under the thorax, and the abdomen
goes over the thorax to the head. In this situation shejumps at short intervals, similar to a
tree in a strong wind. The second reaction is the autotomy of the legs, she loses her legs.
Avoid all physical contact with the legs, ifyou want phasmids with all their legs.
Breeding conditions
The insects needs good climatic conditions, with a good ventilation and low humidity (40-60
% RH). I keep them in 22-25°C. From time to time I sprayed in the cage a little bit of
water. Ifthere is a high humidity (60-90% RH), you will lose the most of your insects due
to diarrhoea and losing the legs.
Foodplants
Bramble is the favourite, raspberry, and strawberry are also eaten. Oak and ivy are also
possible but are not so good for successful breeding.
The study of egg hatching
Lelong (1995) wrote that the hatching date of the nymphs is one month after the laying date.
I can not agree with this, because my results about the hatching dates these eggs showed
something different. I kept 5 females and all were in separate cages. I collected aU laid eggs
Daystohatching
*98*
Figure 2. Incubation time for eggs of PSG 141.
Phasndd Studies 5(1): 15
Ingo Fritzsche
Eggs laid and hatched in February
iStaid
I
B
hatched
j |
February
Eggs laid and hatched in March
Siaid
,
jBhatchedI
Eggs laid and hatched in April
Blaid
I
hatehed
j
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29
April
Eggs laid and hatched in May
Blaid
Bhatched
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31
May
Eggs laid in June
Blaid
Bhatched
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29
June
Figure 3. Number ofeggs laid on each day, and number of those which hatched.
Phasmid Studies, 5(1): 16
PSG 141, GratuUa sp.: a study ofegg layingand incubation
and separated them into small jars for each day. The eggs were kept in separate jars with
the date of laying and the number of the laid eggs on this day. There were the same
conditions in each jar; the conditions were about 50-60% RH and 22-25®C. The eggs
hatched out two months after laying. Most eggs hatched in the morning, between 0600 and
0800.
Table 1 gives the laying and hatching dates for all the eggs from one female. For each
day of the insect*s adult life the table gives the numberofeggs laid, the numberofthose eggs
which hatched, and the dates on which they hatched. The row for the number of eggs laid
is also used to indicate the dates on which the insect became adult ("adu"), dates when
copulation was observed ("cop"), and the date on which it died ("dead"). The data for this
female is similar to the average. From 255 eggs, 92 hatched out, a hatching rate of 36%.
The mean incubation period was 57.4 days, with a range of 44-73 days. These rates varied
very little between the five females. Figure 2 illustrates the variation in incubation time.
Figure 3 shows the number of eggs laid each day, and how many of these hatched,
I can not believe that hatching rates of 80-90% recorded for most species is normal.
Ifyou start culturing a species with 30 or 40 eggs such hatching rates are probably possible,
but mostly you will not get this result with all the eggs laid. In most articles we can find a
high hatching rate stated, but the culture was started by 30 or 40 eggs.
References
Bragg, P.E. (1995) Type species ofphasmid generawith particular reference to the status ofBaculwn Saussure,
1S61, Ranudus Saussure, 1862, and Gratidia SUd, 1875. Phasmid Studies^ 4(2): 11-14.
lielong, P. (1995) Ranudus sp. PSG n® 141. LeMonde des Phasmes^ 30: 26-28,
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